• Part 1: What You See Is Not What the Computer Knows – Read pg. 73 and 74 out loud as a class and discuss the word “redacted.” Continue reading this section (up to pg. 80), using the Conversation Questions Template to write down a question about 3-4 ideas that were important, surprising, or thought provoking. In small groups, discuss your questions.

Redacted: A redacted version of a text is when the key details, or any details are blacked out so an audience cannot see it.




  • Part 3: Hiding Information in Images (pg. 95-99) is called steganography. First, answer the question below, then read the chapter pages as needed to help you complete this activity—you’ll have an opportunity to hide your initials, or some 3-letter word, in an image. Try it, it’s fun!




Short answer:

    1. What is metadata? Give an example of how a piece of metadata could increase the usefulness of an image or document.
      Metadata is information that is about a document. The name of a file is a piece of metadata. This is helpful because it makes the document easy to identify.
    2. What is a model?
      A model is the reproduction of a photo in bit form.
    3. What’s the difference between a raster image and an ASCII representation of a text document?
      A raster image is an image that is represented by breaking it into many small pieces called pixels. This is better for images. ASCII representations break down each character and symbol and assigns them a number, a combination of bits, that are then represented into the document. This is better for documents.
    4. What are filename extensions? What are they used for?
      Filename extensions are how documents get characterized. They are what allow computers to interpret the bits in certain ways (whether or not the bits should be numbers, letters, or colors).
    5. What is lossless representation? What is lossy representation? What are the trade-offs in using each representation?
      A lossless representation allows for the exact image to be rendered with no deviations. A lossy representation renders an image that has some differences. These difference may or may not be visible to human eyes. Lossless pictures are good because they show you exactly what an image is, but are more trouble setting up. Lossy representations miss some details, but that doesn’t matter if the image isn’t supposed to be super high quality.
    6. What is steganography and what is it used for? Describe in your own words the steganographic algorithm used in the activity.
      Steganography is a system where secret messages hide in plain sight in a message. In the activity in the book, the author associated consonants with 0s and vowels with 1s that began words. You would not know to look for that unless you were told, so therefore it is a secret message hidden in plain sight, aka an example of steganography.
    7. What would you have to do to delete a document from your computer so that it could not possibly be read by anyone else? 

      You would have to delete the file, then overwrite any data associated with the file you deleted. Or you delete it, then empty trash to really delete it.

    8. What is free and open source software? Provide an example.
      This basically means anybody can use the software for free. It was made for the public. Apache is an example. It is a web server

Free Response:

  1. How has retouching become a controversial issue? Give an example.
    Retouching is a controversial issue because it manipulates pictures in a way to could distort our reality of certain things. If you distort a picture so that it looks like someone was somewhere where they shouldn’t have been, and they really weren’t, it could make trouble for them.
  2. Would you rather own a camera (or camera phone) with a higher number of megapixels or lower? Explain.
    I’d rather have a camera with more megapixels. Whether or not the lens is good, it still makes images more precise, which is a bonus.
  3. Other than digital images, what might be an example of a computer model? Explain your answer based on the definition of a model.
    Modeling is used when music is captured on a CD. Here, a reality is transmitted into bits, and then creates a slightly different copy of something, in this case a CD.
  4. The code that implements App Inventor is open source and its impact on education is obvious. Find another example of open source software and describe its positive impact on education, business or society.
    I think the code behind Wikipedia would be an open source software. Wikipedia is great because it allows anyone to gain access to information on pretty much anything for free.